Postdoctoral Associate
Ecology and Management of Invasive Plants Program
Department of Natural Resources,
Fernow Hall, Cornell University
Ithaca, NY 14853
Tel.: 607 254 6474; Fax: 607 255 0349; Email: jd259@cornell.edu
Research Interests
I have been involved in biological control of invasive plants using insect natural enemies since 1991. Currently I am evaluating the potential for using leaf beetles in the genus Galerucella from Asia as biological control agents for water chestnuts, Trapa natans. Water chestnut is an introduced Asian floating aquatic plant which has become invasive in the northeastern United States. In its native range, water chestnut is under intense feeding pressure by leaf beetles I am also interested in how biotic and a-biotic factors (including chemical herbicides) affect populations of invasive plants as means to develop integrated management systems.
Approaches
(1) We have collected individuals of various Galerucella species from T. natans and other wetland plants in China.
We will assess their species status and reproductive isolation using morphological and genetic approaches.
(2) We plan to assess preliminary host specificity (feeding, oviposition and larval development) of leaf beetle specimens collected from T. natans and other wetland plants in China. This work will be conducted in close collaboration with Chinese colleagues.
(3) We will map distribution and abundance of T. natans using teams of volunteers and GPS and GIS-based technology. We will also assess presence and abundance of native natural enemies of T. natans in the Finger Lakes Region of New York.
(4) We will develop a standardized monitoring protocol for water chestnut and its associated herbivores before release of any biological control agents.
Projects
Developing biological control of
water chestnut.
Water chestnut, Trapa natans, an introduced Asian aquatic plant, has become invasive in the northeastern United States including New York, Connecticut, Delaware, Maryland, Massachusetts, New Hampshire, Pennsylvania, Vermont, Virginia, and Washington D.C., and Quebec in Canada. Water chestnut can cover ponds, shallow lakes, and river margins displacing native vegetation and limiting navigation and recreation.
Mechanical, manual and chemical control can be successful, but are extremely time consuming, expensive and need to be continued indefinitely. A biological control effort was initiated in the 1990’s for the survey for natural enemies in Northeast Asia and Europe by USDA ARS. Galerucella birmanica (= nipponensis ?) is identified as the most important pest on water chestnut in Asia, causing complete defoliation of entire populations of the plants.
Fig. 4. Larvae and adults feeding on leaves of water chestnut in China
Fig. 5. Damaged water chestnut in a pond, Jiangsu province, China
Thus it would be a promising biological control agent against water chestnut if it is safe to release in the Unites States. However, in China and Japan this beetle was reported to attack watershield (Brasenia schreberi) which is a native plant in North America.
The genus Galerucella is distributed in temperate parts of Asia, Europe, and North America. Among the genus some species are economic important and extremely host specific, such as Galerucella pusilla and G. calmariensis (both species attack Lythrum salicaria), G. tenella (attacking Filipendula ulmaria), G. grisescens (attacking Lysimachia vulgaris), G. quebecensis (attacking Potentilla palustris), G. stefanssoni (attacking Rubus chamaemorus). One exception is the generalist G. nymphaeae, which attacks many different wetland/aquatic plant species and also occurs in North America.
Considering the host specificity of most species in the genus Galerucella and that host plant preferences evolved before morphological differences second during the evolution of host plant specific species, we hypothesized that the species that attacked Brasenia schreberi may be “cryptic” host plant specific new species currently undescribed or unrecognizable using established morphological characters. If leaf beetle specimens collected from T. natans show dietary restrictions to water chestnut and reproductive isolation from leaf beetle specimens collected form Brasenia schreberi, the potential for developing biological control of water chestnut in North America may be more promising. Even if the species feeding on Brasenia schreberil is identical to the species feeding on water chestnut, assessment in detail for the impact of the beetle on native plant flora and ecosystem in North America will be critical to decide its fate in North America.
Key References
Kiviat, E. 1993. Under the spreading water chestnut. Hudsonia 9:1-7
Lu, Z. J., Zhu S. Z. and Z. Chen. 1984. Preliminary studies on the beetle (Galerucella birmanica) – an insect pest of water chestnut and watershield. Sci. Agric. Sinica 5:73-76
Pappers S.M. 2002. Evolution in action: Host race formation in Galerucella nymphaeae, PhD Thesis, University of Nijmegen, Netherlands
Pemberton, R. W. 1999. Natural enemies of Trapa spp. in northeast Asia and Europe. Biological Control 14: 168-180